Handle calibration file headers in `find_calibration_range`

[Tom-Willemsen]

As a user on POLARIS I would like to not get a "calibration over range" warning from eurotherm when using K.txt.

This is due to:

[2025-06-02 16:49:57] sevr=major IN:POLARIS:EUROTHRM_01:A01:CAL:RANGE exception: invalid stod argumentsevr=major IN:POLARIS:EUROTHRM_01:A01:CAL:RANGE exception: invalid stod argumentsevr=major IN:POLARIS:EUROTHRM_01:A01:CAL:RANGE exception: invalid stod argument

Which is in turn because https://github.com/ISISComputingGroup/EPICS-utilities/blame/5b6d7bc41d0dc7ce34482aaf5a17c38b62056301/utilitiesApp/src/find_calibration_range_impl.cpp doesn't look to handle the headers in our calibration files correctly.

discussed in planning 12/06/25 at ~00:35:30